Metal matrix composite

ABSTRACT

An improved metal matrix composite utilizes boron carbide as a ceramic additive to a base material metal. The base material metal is aluminum, magnesium, or titanium, or an alloy thereof, provided in powder form with the balance of the material comprising various trace metals such as chromium, copper, iron, magnesium, silicon, titanium, and zinc. The boron carbide powder comprises 10 to 30% by weight of the metal matrix composition. There is at least one other metal additive. The compositions are useful in a variety of applications where lightweight, strength, stiffness, hardness, and low density are desirable. The compositions are extrudable and weldable.

CROSS-REFERENCE

This is a continuation-in-part of application Ser. No. 08/536,695, filedSep. 29, 1995, which, in turn, is a division of application Ser. No.08/183,728, filed Jan. 19, 1994, now U.S. Pat. No. 5,486,223.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to metal matrix compositions.Such compositions or composites comprise one or more base materialmetals such as, for example, aluminum, titanium, or magnesium, to whichis added a selected percentage of ceramic material to alter theproperties of the base material metal(s) in a positive manner. Strength,hardness, and drawability are increased. Drawability facilitatesfabrication of various articles of manufacture from such compositematerials. More specifically, the present invention pertains to animproved metal matrix composite which, in a preferred embodiment, usesboron carbide as the added ceramic material. The composites result froma novel method of manufacture producing a composite which is lighter,stronger, stiffer, and which has a higher fatigue strength than otheravailable alloys of the base material metal, and which is also lighter,stronger, stiffer, and which has a higher fatigue strength than priorart metal matrices, composites, and particularly those metal matrixcomposites which are of comparable cost.

2. Prior Art

In recent years metal matrix compositions or composites have becomepopular materials for a variety of applications. This new family ofmaterials has become popular because of improvements in stiffness,strength, and wear properties. Basic metal matrix composites are madetypically with aluminum, titanium, or magnesium as the base materialmetal. Then certain percentages of ceramics are added. Typical ceramicsinclude boron carbide, silicon carbide, titanium diboride, titaniumcarbide, aluminum oxide, and silicon nitride. Most known metal matrixcomposites are made by introducing the ceramics into the molten metal.In large production runs of metal matrix composites, the ceramicreinforcement must be wetted by the liquid metal to facilitateincorporation of the reinforcement into the melt. In those metal matrixcomposites using silicon carbide and aluminum, the silicon carbide isthermodynamically unstable in molten aluminum which leads to theformation of aluminum carbide at the interface and increasedconcentration of silicon in the material matrix during thesolidification process. This interface reaction is believed to havedetrimental effects on the mechanical properties of the resultingcomposite by reducing the interface strength and changing thecomposition.

Recently, powder metallurgy consolidation has emerged as a competingmethod of fabricating metal matrix composites by consolidating thepowders by means of hot pressing and conventional powder metallurgyoperations with vacuum sintering used to achieve a high density greenbody. By following certain isopressing and sintering techniques, a 99%theoretical density billet can be achieved.

In the present invention, it has been found that the most desirableceramic candidate for metal matrix composites is boron carbide. Boroncarbide is the third hardest material known and the hardest materialproduced in tonnage. Boron carbide powders can be formed by a variety ofreactions including the carbon reduction of any of several boron-oxygencompounds including boric oxide, borax, boracite, as well as by thedirect combination of the elements. Usually, most commercial boroncarbide is produced in arc furnaces. Boric acid is added together withcarbon in the form of coke and heated to very high temperatures. Anelectric arc is maintained between graphite electrodes inside a furnace.The synthesis reaction is accompanied by the release of large volumes ofcarbon monoxide. Venting and disposal of the carbon monoxide gasconstitutes a major design consideration. Boron carbide is also thelightest of the ceramics typically used in metal matrix compositetechnology, but it is very hard and expensive. Its hardness limits itsextrudability. Thus it would be highly advantageous if it were possibleto produce an improved metal matrix composite which utilizes an advancedceramic such as boron carbide but which, unlike the prior art, resultsin an extrudable composite material that allows easy fabrication ofvarious articles of manufacture so that such resulting articles have thespecific strength and stiffness improvements as compared to equivalentarticles of manufacture using only the base material metals.

SUMMARY OF THE INVENTION

The present invention comprises an improved metal matrix compositewhich, in a preferred embodiment disclosed herein, utilizes boroncarbide as the ceramic additive to a base material metal. Thefabrication process is unlike that of a number of other metal matrixcomposites because it is not made through molten processes. Morespecifically, instead of melting the boron carbide with the aluminum,nickel, zinc, magnesium, titanium, or other base material metal, themetal matrix composite of the present invention begins with the blendingof powders of all the various elements such as by means of a jet millwhich is basically an air blaster used to uniformly mix powderedsubstances and avoid stratification and settling. After the particleshave been sufficiently mixed, they are directed into a die and then intoa cylindrical container where the particulates are subjected toextremely high pressures transforming the elements into a solid ingot.It is from these ingots that the extrusion tubes or other articles ofmanufacture may then be made. The resulting advanced metal matrixcomposites of the boron carbide embodiment of the invention are 60%lighter, 30% stronger, 40-45% stiffer, and 50% higher in fatiguestrength than any of the top of the line 7000 series aluminum alloymaterials. In addition, the inventive material is 7-8% lighter, 26%stronger, 5% stiffer, and has 35-40% greater fatigue strength than mostpopular metal matrix composites available in the prior art.

In one embodiment disclosed herein, the base material metal ispreferably aluminum, magnesium, or titanium, or an alloy thereof,provided in powder form and preferably being approximately 97% pure,with the balance of the material comprising various trace metals such aschromium, copper, iron, magnesium, silicon, titanium, and zinc. Theboron carbide powder is 99.5% pure boron carbide having a particulatesize in the range of 2-19 microns with a mean or average size ofapproximately 8.4 microns. In one typical embodiment of the invention,the metal base material was selected from an aluminum alloy 6061T-6 towhich was added approximately 12% by weight the aforementioned boroncarbide powder to which was added silicon in an amount of 0.1-0.4%, ironin the amount of 0.05-0.4%, and aluminum in the amount of 0.05-0.4%.There is at least one other metal additive. The underlying boron carbidematerial was approximately 77% boron content and 22% carbon content.

A metal matrix composite made from the aforementioned materials inaccordance with the fabrication process of the present invention to bedescribed hereinafter, typically may result in a composite materialwhich exhibits a tensile strength of about 62-108 kpsi, a yield strengthof about 58-97 kpsi, and a modulus of elasticity of about 14.25-14.50Mpsi. Furthermore, the resulting material is approximately as hard aschromoly steel but has a density which is even lower than aluminumalloy.

Importantly, the material of the present invention is readilyextrudable. Ingots of the metal matrix composites of the presentinvention are extruded through a titanium diboride die bearing materialwhich exhibits a significant increase in die insert life. The diebearing material alternatively may be tungsten carbide, tungsten carbidecomposite, boron carbide, carbon nitride, a plasma vapor depositedceramic such as titanium carbide or a chemically deposited ceramic suchas titanium nitride. Furthermore, the present invention is readilyweldable. In fact, the coated boron carbide particulates of the materialdisclosed herein tend to flux and move into the weld pool which createsa very strong weld joint. Thus the present invention is not only highlysuited for the manufacture of various shaped articles, but is alsosuited for interconnecting such articles by conventional weldingprocesses as will be hereinafter more fully explained.

OBJECTS OF THE INVENTION

It is therefore a principal object of the present invention to providean improved metal matrix composite material which exhibits certainadvantageous properties and manufacturability conducive to thefabrication of certain articles of manufacture having improvedcharacteristics such as reduced weight, higher strength, and increasedhardness.

It is an additional object of the present invention to provide animproved metal matrix composite material which is especially adapted foruse as structural members in lightweight applications such as bicycleframes and the like while retaining or improving the strength andhardness at the same or lower relative cost of comparable materials usedin similar structures.

It is still an additional object of the present invention to provide ametal matrix composite material which is stiffer and lighter thanaluminum while being comparable in hardness to steel and extremelyfracture resistant while also being extrudable and weldable, thuspermitting the fabrication of extremely high strength, lightweightstructural members at reasonable cost.

It is still an additional object of the present invention to provide amethod for manufacturing an improved metal matrix composite material toresult in a material having superior hardness, strength, and densitycharacteristics while being extrudable and weldable for use in themanufacture of a variety of structural members which may be readilyconnected to one another such as in bicycle and other vehicle frames andcomponents, engine components, aircraft parts, tooling, sportingequipment such as tennis rackets, badminton rackets, baseball bats,arrows, golf club shafts, and hockey and lacrosse sticks, eyewear,automotive parts, electronic parts, furniture, medical equipment,battery housings, nuclear shielding, marine components, robots, cartsand seats, gourmet cookware, toy casings, high-pressure containers, tanklinings, and armor, for example.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

One preferred embodiment of the present invention uses aluminum alloy asa base material metal and boron carbide as the added ceramic material.In a preferred embodiment of manufacture the aluminum alloy is providedin the form of a metal powder which is blended with jet milled boroncarbide particulates that have been processed and have certain chemicaland particulate size attributes. The boron carbide is preferably atleast 99.5% pure and has a 2-19 micron particle size with an averageparticle size of about 8.4 microns. Included in the boron carbide powderis 0.1-0.4% silicon, 0.05-0.4% iron, and 0.05-0.4% aluminum. Traceamounts of magnesium, titanium, and calcium may also be provided. Twoexemplary semi-quantitative analyses of acceptable boron carbide powdersfor use in the present invention are shown hereinbelow in Tables I andII.

                  TABLE I                                                         ______________________________________                                        B                    77.3%                                                      Si 0.37                                                                       Mg 0.0016                                                                     Fe 0.026                                                                      Al 0.18                                                                       Cu 0.0021                                                                     Ti 0.0088                                                                     Ca 0.0049                                                                     other elements (nil)                                                          C, O.sub.2 (bal)                                                            ______________________________________                                    

                  TABLE II                                                        ______________________________________                                        B                    77.7%                                                      Si 0.14                                                                       Mg 0.0017                                                                     Fe 0.074                                                                      Al 0.13                                                                       Cu ND 0.0002                                                                  Ti 0.017                                                                      Ca 0.0048                                                                     other elements (nil)                                                          C, O.sub.2 (bal)                                                            ______________________________________                                    

The addition of small amounts of pure aluminum, silicon, and iron to thearc furnace during the production of boron carbide, such as by thereaction of boric acid and carbon, has been found to improve the boroncarbide for use in this metal matrix composite. These elements areusually present in an amount less than 3.0% by weight. These metalelements do not go out of solution. They stay in the boron carbide andprovide a chelating opportunity for the base material aluminum. Theseadditional metals form an intermetallic chemical bond with the mainmetal alloy. However, it will be understood that the aforementionedadditions of pure aluminum, silicon, and iron, may not be the onlymetals which can be used for the aforementioned purpose. By way ofexample, virtually any low temperature reacting metal that forms anintermetallic phase below the processing temperature of the metal matrixcomposite ingot would be usable in the present invention for the purposeindicated.

A typical relative weight contribution of the boron carbide powder andbase material metal powder is 10-30% of the former and 70-90% of thelatter depending upon the specific characteristics desired for thefinished product. Several typical formulations are as follows:

1. A metal matrix composite of aluminum alloy 6061 base metal materialand 20 weight % boron carbide. This composite material is extrudable andexhibits a tensile strength of 65.3 kpsi and a yield strength of 59.8kpsi. It is useful for structural components for transportation vehiclesand computer discs. It has stiffness and strength.

2. A metal matrix composite of aluminum alloy 6061 base metal materialand 25 weight % boron carbide. This composite material is extrudable andexhibits a tensile strength of 71.9 kpsi and a yield strength of 62.6kpsi. This formulation is useful for brake discs and marine castings. Ithas corrosion resistance and wearability.

3. A metal matrix composite of aluminum alloy 6061 base metal materialand 30 weight % boron carbide. This composite material is extrudable andexhibits a tensile strength of 62.3 kpsi and a yield strength of 58.4kpsi. The formulation may be used for structural stiffness for marineapplications or nuclear shielding since it has strength and corrosionresistance.

4. A metal matrix composite containing aluminum alloy 7091 base metalmaterial and 20 weight % boron carbide. This composite material exhibitsa tensile strength of 98.6 kpsi, a yield strength of 89.2 kpsi, and isextrudable. This composition has utility for spacecraft and satellites.It has low thermal expansion and high tensile strength.

5. A metal matrix composite containing aluminum alloy 7091 base metalmaterial and 30 weight % boron carbide. This composite material exhibitsa tensile strength of 107.9 kpsi, a yield strength of 96.4 kpsi, and isextrudable. The material is useful for containers for high pressure andcorrosive materials. The material has high strength and corrosionresistance.

After the boron carbide has been jet milled to the selected particulatesize and with the aluminum alloy powder blended together in a doublechamber "V" blender, for two and one-half hours at 20 to 30 RPM in aninert gas, the powders are degassed at 200 degrees Centigrade for onehour in a vacuum of 5 to 8 Torr and then placed in a latex bag andisopressed at 65,000 psi. The isopress bag resembles the shape of theingot that is to be extruded. The latex bag is degassed and clamped off.The maximum pressure is held for at least a one minute soak. Theresulting ingots are removed from the bag and placed into a vacuumfurnace to undergo a sintering cycle in accordance with the followingpreferred embodiment of the process of the present invention.

First, the ingots are heated from room temperature to 300 degreesCentigrade over a twenty minute ramp period during which time binder andwater are burned off. The ingots are then heated to 450 degreesCentigrade over a fifteen minute ramp period during which the remainingbinder is burned off. The ingots are then heated to 625 degreesCentigrade over a forty minute ramp period during which the temperatureincreases accordingly. At 625 degrees Centigrade the ingot is held andsoaked at that temperature for 45 minutes during which close grainboundaries are formed. The ingot is then cooled from 625 degreesCentigrade to 450 degrees Centigrade over a twenty minute period bymeans of a nitrogen gas backfill. Finally, the ingots are cooled to roomtemperature at a rate not faster than 40 degrees Centigrade per minuteagain using nitrogen gas. The ingots are then turned down by a metallathe to bring them into an extruding shape with a typical selectedouter diameter of between 31/2 and 7 inches to a tolerance of 15,000thsof an inch. The ingots are then available for extrusion.

Extruding the metal matrix composite of the present invention firstinvolves preheating the ingots in a resistance furnace for a minimumperiod of one hour at 555 degrees Centigrade. This is normally done intwo steps. First the ingots are heated to 315 degrees Centigrade in aholding furnace and then heated to a higher temperature and held untilthe ingot temperature reaches 555 degrees Centigrade. The ingots arethen loaded directly into a container or chamber from the furnace. Thechamber temperature should preferably be 488 degrees Centigrade. Theface pressure within the chamber depends upon the type of extrusiondimensions that are desired. Typically, the pressures used are 15-20%higher than extrusion pressures used for 6061 aluminum ingots. Forexample, for a 31/2 inch outer diameter billet made of the metal matrixcomposite of the present invention, 3,500 psi peak (break out) pressureis typically used and results in an extruding pressure of about 3,000psi. The speed of the extrusion could be an average of 15-30 feet perminute and the exit temperature should be 20 degrees Centigrade coolerthan the container temperature. The speed of the ram used for theextrusion should run 31/2 inches every minute on a typical 31/2 inchouter diameter ingot.

Although the present invention may be extruded in conventional dies, ithas been found that for maximum die insert life, a die bearing materialmade of titanium diboride is preferred. The titanium diboride diebearing material is preferably hot pressed and then electrodischargemachined to the appropriate size. A small amount of boron carbide may beused to increase the hardness of the die. Typically, the die is made of99.5% pure titanium diboride in an amount equal to 92-98% by weight, theremaining fraction being 99.5% pure boron carbide having particulatesizes less than 10 microns. The hot press cycle for manufacture of thedie bearing material is preferably done at 1,800 degrees Centigradeusing a 3,500 psi pressure with the pressure and temperature maintaineduntil a zero drop in ram travel is obtained.

The extruded metal matrix composite provides the greatest benefit if itis heat treated using a T6-type heat treatment which comprises two hoursat 530 degrees Centigrade with a cold water quench and an artificialaging at 177 degrees Centigrade for ten hours. All welding, however, hasto be accomplished before heat treatment is applied. Unlike other metalmatrix composites which contain silicon carbide and aluminum oxide wherewelding can be a problem, the metal matrix composite of the presentinvention is readily weldable. Other metal matrix composites formaluminum carbides as brittle components of a weld. Aluminum carbides areformed from the chemical reaction of aluminum and silicon carbide.Because of the surface area of the aluminum oxide particulates and metalmatrices, clumping and dewetting occurs. These brittle components andparticulates clump together thereby greatly decreasing the strength of aweld body. The metal matrix composite of the present invention does nothave these problems. The coated boron carbide particulates tend to fluxand move into the weld pool which creates a very strong weld joint.Because boron carbide particulates have a melting point of 2,450 degreesCentigrade, the boron carbide is chemically inert at aluminum processingtemperatures.

Depending upon the ratio of boron carbide to aluminum and also dependingupon the particular aluminum alloy used as the base material metal, theresulting material has a density of less than 2.70 grams per cubiccentimeter which is lower than aluminum 6061. One formulation has adensity of 2.52 grams per cubic centimeter. The resulting material alsohas a tensile strength of 62-108 kpsi, a yield strength of 58-97 kpsi, amodulus of elasticity of from 14.25-14.50 Mpsi, and is extremelyfracture resistant and more predictable than other composites.Furthermore, the resulting material of the present invention has ahardness which is comparable to that of titanium and chromoly steel, buta density which is roughly a third of steel and roughly 60% of titanium.

Two advantageous products made from the metal matrix composites of theinvention are bicycle frames and golf club heads. Bicycle frames madefrom extruded and welded tubing of the inventive material are lighter,stiffer, and stronger than comparable bicycle frames made of moreconventional materials such as aluminum, steel, or titanium. In golfclubs, the lower density of the inventive material allows for thickerwalled heads, better weight distribution, balance, and aerodynamics.Furthermore, a larger "sweet spot" is possible in tournament legalclubs.

Some particular exemplary applications are as follows:

1) Discs used as substrates for hard drives in computer systems.

2) Extruded structural components for various transportationvehicles--e.g. bicycles, motorcycles, aircraft, militaryvehicles--including frames, interior floors and panels, handle bars,propulsion structures, flight control systems, fuel management systemsand landing gear.

3) Cast structural components and auxiliary parts for varioustransportation vehicles--bicycles, motorcycles, aircraft, and autowaterpumps, bicycle cranks, disc brakes, and landing gear.

4) Housings for batteries where light weight and corrosion resistanceare important.

5) Housings for electronic "boxes" for numerous applications whereweight, high impact strength, and low thermal expansion areconsiderations--e.g., stamped casings for cellular phones, notebookcomputers, portable electronics.

6) Extruded structural parts of sporting goods equipment, e.g., tennisrackets, badminton rackets, baseball bats, arrows, golf club shafts,eyeglasses, oars, hockey sticks, billiard cues, ping pong paddles,lacrosse sticks, racquet ball rackets and basketball stanchions.

7) Cast sporting goods components such as golf club heads, archeryequipment, ball throwing equipment, camping equipment, exerciseequipment, fishing reels, hiking and mountaineering accessories, skatetrucks, locks, optical frames, rowing equipment, water skis andsnowboards.

8) Spray coatings for thermal, abrasive, and other forms of protection.

9) Nuclear shielding applications.

10) Internal combustion engine components--engine blocks, pistons, rods,valves, camshafts, and crankshafts.

11) Marine applications for extruded and cast material--spars,turnbuckles, propellers, and portholes.

12) Robotics applications for extruded and cast material where lightweight, strength and fatigue resistance are critical.

13) Substrates for high power electronic components.

14) Structures for carts, amusement rides, ski lifts, elevators,escalators, moving sidewalks, trams and other general people movingpurposes.

15) Gourmet cookware, knives, and other consumer niche markets.

16) Casings and parts for toys.

17) Armor for vehicles, personal security.

18) High pressure containers; e.g., gas storage, power transformers.

19) Casings and bits for down-hole drilling assemblies in oilprospecting.

20) Large structures where weight and toughness is important--e.g.,inner hulls for oil tanker ships.

21) Portable tools of all kinds, for industrial, commercial, medical andconstruction use, where light weight and toughness are paramount.

22) Medical applications--e.g., prosthesis, braces, medical instrumentsand tools, where strength and light weight are important.

23) Dental applications--drill bits.

24) Transducers--bases and other parts of sensors for temperature andother parameters.

25) Channels, attenuators, combiners and other components of microwavenetworks and transmission systems.

26) Structures for spacecraft and satellites where low thermal expansionand light weight are key features.

Although described herein are preferred embodiments of the materialcomposition and method of fabrication of the present invention, theinvention may have other applications and embodiments. Suchmodifications as are within the knowledge of those skilled in the artare encompassed by the spirit and scope of the invention.

I claim:
 1. A metal matrix composite for structural applications,comprising:a base material metal and boron carbide in a ratio ofapproximately between 3 and 10 to 1 by weight, the boron carbide beingsubstantially homogeneously distributed among the metal, forming closegrain boundaries therewith; and less than about 3.0% by weight of atleast one metal having an intermetallic phase temperature lower than themelting point of the base material metal, the at least one metalproviding a chelating opportunity for the base material metal, whereinthe composite is extrudable and weldable, and the composite undergoesyield by plastic deformation without brittle fracture.
 2. A metal matrixcomposite comprising,a base material metal and boron carbide in a ratioof approximately between 3 and 10 to 1 by weight, the boron carbidebeing substantially homogeneously distributed among the metal, formingclose grain boundaries therewith, wherein the base material metal isselected from the group consisting essentially of magnesium and alloysof magnesium; and less than about 3.0% by weight of at least one metalhaving an intermetallic phase temperature lower than the melting pointof the base material metal, the at least one metal providing a chelatingopportunity for the base material metal, wherein the composite isextrudable and weldable.
 3. The composite recited in claim 1, whereinthe base material metal is selected from the group consistingessentially of aluminum, titanium, and alloys thereof.
 4. The compositerecited in claim 1, wherein the composite has a density of about 2.5grams per cubic centimeter.
 5. The composite recited in claim 1, whereinthe composite has a tensile strength of about 62-108 kpsi.
 6. Thecomposite recited in claim 1, wherein the composite has a yield strengthof about 58-97 kpsi.
 7. The composite recited in claim 1, wherein thecomposite has a modulus of elasticity of about 14-15 Mpsi.
 8. Thecomposite recited in claim 1, wherein the base material metal isaluminum alloy 6061, boron carbide is present in a ratio ofapproximately 5 to 1 by weight, and the composite has a tensile strengthof about 65 kpsi and a yield strength of about 60 kpsi.
 9. The compositerecited in claim 1, wherein the base material metal is aluminum alloy6061, boron carbide is present in a ratio of approximately 4 to 1 byweight, and the composite has a tensile strength of about 72 kpsi and ayield strength of about 63 kpsi.
 10. The composite recited in claim 1,wherein the base material metal is aluminum alloy 6061, boron carbide ispresent in a ratio of approximately 3 to 1 by weight, and the compositehas a tensile strength of about 62 kpsi and a yield strength of about 58kpsi.
 11. The composite recited in claim 1, wherein the base materialmetal is aluminum alloy 7091, boron carbide is present in a ratio ofapproximately 5 to 1 by weight, and the composite has a tensile strengthof about 99 kpsi and a yield strength of about 89 kpsi.
 12. Thecomposite recited in claim 1, wherein the base material metal isaluminum alloy 7091, boron carbide is present in a ratio ofapproximately 3 to 1 by weight, and the composite has a tensile strengthof about 108 kpsi and a yield strength of about 96 kpsi.
 13. Anextrudable and weldable metal matrix composite for structuralapplications, formed by the process of:a) blending powders of a basematerial metal, boron carbide, and at least one metal having anintermetallic phase temperature below the melting point of the basematerial metal, wherein the boron carbide constitutes about 10-30% ofthe powders by weight and the at least one metal constitutes less thanabout 3.0% of the powders by weight, the at least one metal providing achelating opportunity for the base material metal; b) degassing theblended powders; c) isopressing the blended powders at a pressure of atleast 65,000 psi; d) heating the isopressed powders up to at least 625degrees Centigrade over a selected period of time; e) configuring theisopressed and sintered powders to form a composite material; f) heattreating the composite material to form a composite which yields byplastic deformation without brittle fracture; and g) at least one ofextruding the composite material and welding the composite material. 14.A metal matrix composite formed by the process of:a) blending powders ofa base material metal, boron carbide, and at least one metal having anintermetallic phase temperature below the melting point of the basematerial metal, wherein the boron carbide constitutes about 10-30% ofthe powders by weight and the at least one metal constitutes less thanabout 3.0% of the powders by weight, the at least one metal additiveproviding a chelating opportunity for the base material metal, whereinthe base material metal is selected from the group consistingessentially of magnesium and alloys of magnesium; b) degassing theblended powders; c) isopressing the blended powders at a pressure of atleast 65,000 psi; d) heating the isopressed powders up to at least 625degrees Centigrade over a selected period of time; e) configuring theisopressed and sintered powders to a desired shape; and f) heat treatingthe desired shape.
 15. The metal matrix composite recited in claim 13,wherein the base material metal is selected from the group consistingessentially of aluminum, titanium, and alloys thereof.